What are we to make of the apparently increasing effects of MLDA exposure with age shown in figure 1? The regression models illustrated in figure 2 and supplementary table 4 suggest that after controlling for year of birth and state fixed effects, the MLDA effects are probably similar across age. However, an increasing effect with age would in fact be possible. For example, MLDA exposure might affect the persistence of alcohol problems, but not the incidence in early adulthood. It is also possible that DSM-IV criteria are better at discriminating ‘problem’ use from ‘normal’ use when evaluation occurs at later ages.
